Income Taxes - Korean and Singapore subsidiary commitments (Detail) - USD ($) $ / shares in Units, $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Income Tax [Line Items]
Undistributed Earnings of Foreign Subsidiaries	$ 35.9
Korea Tax Authority [Member]
Income Tax [Line Items]
Income tax benefit estimate attributable to the tax status of subsidiary		$ 4.0	$ 7.4
Income tax expense benefit per diluted share		$ 0.03	$ 0.05
additional effective tax rate benefit		$ 4.3
Inland Revenue, Singapore (IRAS) [Member]
Income Tax [Line Items]
Income tax benefit estimate attributable to the tax status of subsidiary	$ 5.8	$ 6.3	$ 4.7
Income tax expense benefit per diluted share	$ 0.04	$ 0.04	$ 0.03
additional effective tax rate benefit	$ 3.3	$ 3.6	$ 12.4